Orientation-Patterned GaAs (OPGaAs) waveguide structures are promising devices for mid-infrared (IR) nonlinear conversion since tight optical confinement to a highly nonlinear medium allows high-frequency conversion efficiency of CW sources. The use of OPGaAs for IR and THz generation has been successfully realized by using MBE-grown templates. (See, Yu, X., Scaccabarozzi, L., Levi, O., Pinguet, T. J., Fejer. M. M. and Harris Jr., J. S., “Template design and fabrication for low-loss orientation-patterned nonlinear AlGaAs waveguides pumped at 1.55 μm”, J. Cryst. Growth, 251, April 2003, pp. 794-799.) However, the templates so created had a periodic depth variation between alternate regions of differing crystalline orientation, the so-called trench depth, of ˜1500 Å. Since crystal growth on the templates was highly anisotropic the result was a top surface composed of ˜50 μm-tall triangular features that occurred periodically.
OPGaAs templates have also been obtained using wafer diffusion bonding and selected-layer removal. (See, Oron, M. B., Shusterman, S, and Blau, P., “Periodically oriented GaAs templates and waveguide structures for frequency conversion”, Proc. SPIE, 6875, February 2008, 68750F.) Using this technique, the trench depth was reduced to values of ˜900 Å. The crystal growth technique used was metal-organic vapor-phase epitaxy (MOVPE), which transferred the template's periodic depth variation to the grown layers. Ridge-type waveguides were subsequently fabricated on templates of 900 Å trench depth, and the waveguide-loss coefficient, αw, at a wavelength of 1.6 μm, was measured to be in the 3-5 dB/cm range.
Using templates of 600-800 Å trench depth, the αw value was lowered to typical values of 1.3-1.5 dB/cm at 1.6 μm wavelength, while the periodic trench depth was still transferred to the waveguide layers with some variation in the channel profile. (See, Oron, M. B. Blau, P., Pearl, S, and Katz, M., “Optical parametric oscillation in orientation patterned GaAs waveguides”, Proc. SPIE, 8240, February 2012, 82400C.)